Originally Posted by EWRflyr

As cal73 stated, a modification to your pairing results in a different subsequent letter at the end. Now in all (limited) fairness, not all modifications mean that a reserve is getting hosed. Sometimes a modified pairing with a letter results from a change in a flight number or hotel as an example, even for line holders. For a reserve though it generally means something has been added to the pairing.

As was stated above, you could start out with V5038 as a three-day but along the trip or when you return they have either changed it or added to the end of it for you to go on if your next days are movable days off. So, there are reserves out there flying pairings that have reached P, Q, R and even more. One captain I flew with said when he used to be on reserve he hit a double letter change (i.e. after Z). My mouth dropped when he said that. Has to be a record.

A reserve can be gone from base all the way up until the next set of IMMOVABLE days if they so desire. All that is required is a 24-hour break someplace downline. This is routine for international, but for domestic operations all the contract says is that the company will TRY to give you a calendar days off in base but it is not required to do so.

So, a reserve could leave on a trip and as long as the company can look back and find a 24-hour layover in the past 6 days they can continue to add to the pairing, respecting all other flight-time/duty-time and rest requirements of the FARs. This means days off can be continuously rolled to the next available days until you come up against IMMOVABLE days off. There could be circumstances where movable days off are at the end of the month and the company can roll those days off out of the current month, but they must be restored in the next month (with no reduction in pay for the next month).

The horror stories of reserve are MOSTLY, but not entirely, related to summer flying. The reserve rules themselves will apply all year long, however things seem to calm down from September to May with the exception of those major snow storm situations.